Thefts of smartphones make up 30 percent of robberies in the U.S., according to supporters of the proposed laws. Many are believed to be crimes of opportunity, committed when a smartphone user is on their phone and not paying attention to their surroundings. The thefts can be violent, with the victim being beaten or threatened with a knife or gun. In a handful of cases, victims have been killed for their phones.

Law enforcement officials believe that by having a mandatory kill switch incidents of theft will fall because most phones will quickly be made useless and therefore have no or little commercial value.

With pressure mounting at the state and federal level, that attitude appears to be shifting. Last week, executives of Verizon Wireless, T-Mobile USA and C Spire Wireless told a congressional hearing that they are willing to install such a system.

Under the proposed laws, only the consumer would have the ability to disable their phone.

Apple already has such a technology in devices running its iOS 7 operating system. The activation lock accomplishes all of the kill-switch features but requires the user to switch it on. The proposed law would make it the default setting and users' action would be required to switch it off.